It is known to use apparatus for regulated delivery of a gas, notably respiratory assistance apparatus, comprising:
a fan essentially constituted by a motor, an impeller driven by that motor and a fan scroll containing that impeller, the motor being contained in a motor casing having a first end connected to the fan scroll and a second end situated on the side opposite the fan scroll; and
a casing receiving the fan, defining around that fan a space for flow of the air for cooling the fan, this space having an air inlet situated at said second end of the motor casing.
Apparatus of this type is described for example in published patent application No FR 2 908 482 in the name of the applicant.
Such respiratory assistance apparatus must be able to operate over a wide range of flow rates, and in particular be capable of delivering a low flow rate of gas (for neonatal or paediatric use). The type of fan motor used in such apparatus, and likewise the fast rotation of that motor, induce high heating of the motor, particularly when the fan is delivering a low flow rate.
This heating is accentuated if the motor casing is closed at said second end by a transverse wall including a lower bearing guiding the shaft of the motor. To prevent flow of air under pressure through this bearing, which would have the effect of drying out the grease in the bearing and polluting the air that has passed through the bearing, this lower transverse wall is solid and completely closes the lower portion of the motor casing, which is not favourable for good cooling of the motor.
Generally speaking, much apparatus of this type suffers from motor cooling problems, which impacts on their performance and their longevity.